The extreme to which he is taking things and the level of rigor he is (seemingly) applying, are the differences I see. He has a lot more time and resources at his disposal than most wellness hackers.

Isn't this just marketing, though?

Doesn't seem like it. He was doing most of what he claims years before he marketed anything. I remember him on Lex Friedman years ago talking about only eating one meal per day, eating as healthy as possible, optimizing his sleep, etc.

The difference that I'm seeing personally and the initial appeal was that he was more open about the science and the results of it. If you go through the site you can see pretty good documentation about different supplements and what their intended purpose was. However, I do think some of the luster of the open-source model he had kind of disappeared when he started selling products which is a double edged sword in the sense that it does somewhat certify the quality of the product but also chips at his ethos.